This invention relates to belts used in continuously variable transmissions (xe2x80x9cCVTxe2x80x9d), and more particularly to side drive CVT belts comprising cogs or teeth having transverse reinforcement.
It is well known in the art that a gear type transmission may be used for running a motor vehicle, motorcycle or the like. However, gear type transmissions generally have a fixed number of gears. They are usually designed to operate most efficiently in one of the gears, leaving the others to cause the engine to run at less efficient operating points. Consequently, for the purpose of improving efficiency a continuously variable transmission, CVT, is preferable. Various types of belts have been developed for use in continuously variable transmissions.
Generally, the CVT Belts have a silhouette similar to that of a conventional V-belt. In particular, they are broad at the top and narrow at the bottom and designed to fit between the sheaves of a pulley defining an angular groove. The pulley on which the belt is trained comprises a moveable sheave and a fixed sheave, both having a truncated cone shape. Generally, one of the sheaves moves while the other remains fixed.
Moving one sheave in relation to the other varies the effective diameter xcfx86 of the pulley within which the belt operates. Belt speed is a function of the effective diameter of the pulley which is in turn a function of the axial position of the sheaves relative to each other.
CVT type belts in the prior art include belts comprising a plurality of blocks mounted transversely on a tensile member as well as monolithic metal belts and elastomeric belts. Certain forms of cog type belts are also known.
Representative of the art is U.S. Pat. No. 4,493,681 to Takano. Takano discloses a V-section cog belt having rigid metal reinforcing members in each cog extending transversely across the belt. The metal reinforcing members provide transverse rigidity to the belt.
Since the Takano belt operates in contact with the sheaves of the CVT pulley, it is desirable to reduce wear between the belt sides and the pulley as much as possible. This reduces heating, which enhances belt life. Metal rods in direct contact with the sheaves, as taught in Takano, cause undue heating and wear between the belt sides, the reinforcing rods and the pulley sheave surfaces. The use of metal rods also increases the rotating mass and cost of the belt. Further, during fabrication the rods may become misaligned in each tooth. This will cause some of the rods to bear a disproportionately higher load than the adjacent rods. This may result in premature failure. of the overloaded rods and eventually the belt.
Further representative of the art is German patent application DE 197 47 173 A1. It discloses a toothed elastomeric v-belt having transverse teeth. Each tooth having a transverse bore. Each bore may contain tube sections or bar sections. The bore provides a path for cooling air flow through the tooth. However, such bores decrease the compressive strength of each tooth. The application is appropriate for synchronous pulley systems wherein the belt teeth cooperate with conjugate surfaces in a pulley or pulleys.
What is needed is a transverse reinforced CVT belt having a non-metallic or thermoplastic, thermoset or composite transverse reinforcing member in each tooth. What is needed is a transverse reinforced CVT belt having alignment pegs on each transverse reinforcing member. What is needed is a transverse reinforced CVT belt having transverse reinforcing members with sufficient stiffness in the anticipated temperature range. What is needed is a transverse reinforced CVT belt having transverse reinforcing members with a low mass density. The present invention meets these needs.
The primary aspect of the invention is to provide a transverse reinforced CVT belt having a thermoplastic, thermoset or composite transverse reinforcing member in each tooth.
Another aspect of the invention is to provide a transverse reinforced CVT belt having centering pegs on each transverse reinforcing member.
Another aspect of the invention is to provide a transverse reinforced CVT belt having transverse reinforcing members with sufficient stiffness in the anticipated temperature range.
Another aspect of the invention is to provide a transverse reinforced CVT belt having transverse reinforcing members with a low mass density.
Other aspects of the invention will be pointed out or made clear by the following description of the invention and the accompanying drawings.
The invention comprises a cog type belt having a plurality of transverse teeth on an inner surface. The belt comprises an outer extensible elastomeric layer, an inner compression layer and a tensile member. Each tooth further comprises a non-metallic or plastic transverse member, pillar or rod that extends across the width of each tooth. The opposing outer surfaces of each transverse member are inclined to each other and each end approximately equates to an outer surface of the belt body elastomeric. A compressive load between the sheaves is carried by the rod and the sidewall in proportion to the modulus of each component. The transverse members have pegs or legs that allow proper spatial orientation of each transverse member in each tooth during the fabrication process, thus assuring proper operating characteristics, including proper alignment within a pulley.